(i) Field of the Invention
The present invention relates to an image forming apparatus configured to form an electrostatic latent image by exposing an electrically charged photo conductor with a laser, and a process cartridge and an exposure scanning unit for use in such an image forming apparatus.
(ii) Background Art
An example of a conventional image forming apparatus is a so-called tandem color laser printer in which a plurality of photoconductor drums corresponding to a plurality of printing colors are arranged in parallel along belt members, such as a paper conveyor belt and an intermediate transfer printing belt.
In such a color laser printer, the surface of each rotatingly driven photoconductor drum is electrically charged evenly by a charger. When the electrically charged surface of each photoconductor drum is irradiated with a laser light in a scanning manner at a high speed by a scanner unit, an electrostatic latent image is formed. Then, the electrostatic latent image is developed with toner by a developing unit to form a toner image on the surface of each photoconductor drum. In this case, since the toner used for the developing unit is a consumable item, at least a process cartridge having the developing unit as a constituent element is usually configured to be attachable/detachable to/from a printer main body.
In such a tandem color laser printer, the chargers, the scanner units, the developing units, and the like for forming toner images on the surfaces of the respective photoconductor drums are required to be arranged so as to face the surfaces of the respective photoconductor drums. Since the scanner units and the developing units are relatively large because of their structures, arrangement of scanners and developing units alternately so as to face a plurality of photoconductor drums requires a long distance between the photoconductors. This will lead to a problem of an increased size of the color laser printer.
To shorten the distance between the photoconductors, a scanner unit may be arranged so as to face the surfaces of photoconductor drums with developing units located therebetween, as disclosed in the Publication of Unexamined Japanese Patent Application No. 2003-15378, such that the scanner unit is not located between the developing units.